An intake system having a port and a surge tank in a multiple cylinder internal combustion engine of a car or the like is provided with a partition that divides the inside of the surge tank into two sections and a butterfly valve is attached to a position in which, for example, a portion of the partition is cut out. A butterfly valve includes a valve element that is switched to a state where the two sections divided by the partition are in communication (hereinafter, referred to as an “open valve state”) or a state where the two sections are partitioned (hereinafter, referred to as a “closed valve state”) by a rotation, a valve body that supports the valve element, and a sealing material for sealing between the inner circumferential edge of the cut out portion of the partition and the outer circumferential edge of the valve body (for example, PTL 1).
The resonance frequency of the intake system is changed by switching the valve element to an open valve state or a closed valve state, and a supercharging effect can be obtained in wide operation ranges of the engine. If the leakage of the air between the two sections is increased in the closed valve state, the expected resonance frequency is not generated in the intake system of the engine and the supercharging effect is degraded, resulting in the deterioration of the performance of the engine.
In the intake control valve (butterfly valve) disclosed in PTL 1, a sealing material made of an elastic material is attached to the circumferential edge portion of a valve holder. When the valve holder is mounted in the partition, the sealing material fits onto a groove portion provided on the inner circumferential edge of the partition. Moreover, a rubber sealing material is attached to the outer circumferential edge portion of the valve element attached to the valve holder and seals a gap between the valve element and the valve holder in the closed valve state. Accordingly, the leakage of the air between the two sections is suppressed in the closed valve state.